Fluid pressure cylinder



y 1962 J. w. NORWOOD 3,033,169

FLUID PRESSURE CYLINDER Filed Feb. 27, 1961 INVENTOR.

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United States Patent 3,033,169 FLUID PRESSURE CYLINDER John W. Norwood, Cottage Grove, reg., assignor to Kimwood Machine Co., Cottage Grove, Oreg. Filed Feb. 27, 1961, Ser. No. 92,084 1 Claim. (Cl. 12138) The present invention relates to fluid pressure actuated, reciprocating-type motors, and has as its primary object the provision of improved means for cushioning or slowing down the speed of movement of the movable piston as it nears the end of its stroke.

As conducive to a clearer understanding of the invention, it may here be pointed out that it has hitherto been the practice to provide fluid actuated reciprocating motors with some means for cushioning or slowing down the speed of the moving element to reduce the shock of stopping at the end of a stroke. This precaution is especially necessary in situations where heavy loads are moved so as to prevent serious damage by jarring or jolting of the machinery. The essential feature of the present invention resides in a novel cushion structure to provide a long lasting assembly effectively to slow down or cushion the piston assembly of a pneumatic cylinder at or near the end of its stroke. While cushions of various types for piston and cylinder assemblies are generally known, the specific cushioning apparatus to be disclosed herein involves novel structure for more effectively cushioning the piston as it approaches the end limits of its movement. This is accomplished by providing a lateral exhaust outlet spaced from the cylinder head whereby the piston as it passes the exhaust outlet entraps a quantity of fluid between the piston and cylinder head. The cylinder head is provided with an inlet opening or passage having a check valve therein preventing outflow of fluid therefrom while permitting inflow. A metered bypass passage is provided which bypasses the check valve thereby enabling controlled escape of the entrapped fluid thereby effecting a progressive slow down of the piston. Control of the bypass passage is accomplished by an adjustable needle valve and the entire assembly is quite compactly arranged.

The amount of cushioning required is dependent upon the load being moved and the speed of the piston stroke.

A further object of this invention is to provide a fluid pressure motor of the character described, designed and assembled so that it will be durable, efficient, and inexpensive to manufacture.

Another object of the invention is the provision of piston rings for trapping air within the motor to assist in cushioning the stroke. Another object of the invention is the provision of neoprene cups which do not pass over the exhaust ports during their movement in the cylinder barrel.

Still another object of this invention is the provision of a novel head telescoped over the end of the cylinder barrel support while cushioning the stroke of the piston.

The invention resides in constructions and combinations and arrangements of parts, and further objects and advantages will be apparent to those skilled in the art to which it relates from the following description of the preferred embodiment described with reference to the accompanying drawing which illustrates a fluid pressure actuated motor.

In the drawing:

FIGURE 1 is a longitudinal sectional view of the fluid motor.

FIGURE 2 is a transverse sectional view taken along lines 2-2 of FIG. 1.

Similar reference characters refer to similar parts throughout the several views of the drawing.

Referring now to the drawing, reference numeral 1 loads.

3,033,169 Patented May 8, 1962 designates generally a fluid pressure actuated motor. The motor 1 comprises a cylinder assembly 2, including a hollow cylinder proper 3, closed at its opposite ends by heads 4 and 5 to form a cylinder bore 6 and a piston assembly 7. Assembly 7 comprises a piston 8 located in the cylinder bore and connected to piston rod 9 which extends to the exterior of cylinder bore 6 through an aperture 10 in head 5 and terminates into a threaded shaft. The head 5 through which piston rod 9 extends is provided with a self-sealing chevron-type rod packing 11. Adjacent packing 11 is positioned a suitable rod guide bushing 12, which is preferably made from bearing bronze. The construction of the packing described is designed to prevent the escape of fluid around the piston rod. Suitable bolts 13 maintain bushing 12 in position.

It will be noted that cylinder heads 4 and 5 are preferably of cast steel, designed for handling extreme shock The head covers the cushioning zone at the end of the stroke, giving support to this critical pressure area. By use of this construction the tube cannot swell or rupture causing a loss of the cushion.

Cylinder proper 3 is preferably constructed of hard drawn brass, which is corrosive resistant and maintains a smooth bore to facilitate a leakproof packing contact.

In the flanges of heads 4 and 5 are provided in recessed grooves seal rings 14 and 15 which are preferably 0 rings of neoprene composition. Positioned circumferentially between rings 14 and 15 is a recessed area 16, which communicates with the cylinder proper 3 by Way of ports 17. Positioned Within a provided chamber within heads 4 and 5 .is a ball check valve assembly 18 which maintains a large opening for full power and fast starts at the beginning of the piston stroke. Also positioned in heads 4 and 5 is a needle valve assembly which permits variation in slowdown at the end of the piston stroke. Passages 18' are provided in cylinder heads 4 and 5 through which operating fluid passes during a piston stroke. The passages 18' also allow the operating fluid trapped in the end of the cylinder 3 at the end of a piston stroke to communicate with the needle valve assembly and be bled off.

Piston 8 is provided with piston rings 14' which are placed in a circumferential groove in the piston. Suitable thread screw means 20, maintains a piston follower 21, in close contact with piston 8. Disposed between the body portion of piston follower 21 and piston 14, is a piston packing assembly having a back up ring 22 positioned between neoprene cups 23. A lock nut 9' engages the thread of piston rod 9 and holds piston 8 thereon.

The needle valve assembly comprises internally threaded bushings 24- secured in cylinder heads 4 and 5, and threaded needles 25 tapered at one end adjustably mounted therein. The needles 25 can be adjusted with respect to orifices 26 to permit change in the rate of bleed off of fluid trapped in the end of cylinder 3 at the end of a piston stroke.

In operation, fluid pressure is introduced into one end of the cylinder and forces it to the other end of the cylinder. The piston rod 9 moves with the piston 8, which is connected to apparatus (not shown) that requires a push or pull to do its job. As the fluid pressure enters one end of the cylinder, external valve (not shown) exhausts the air from the opposite end of the cylinder and the piston 8 is forced rapidly down the barrel 3. As the piston 8 nears the end of its stroke, one of the piston rings 14', depending upon which direction the piston is moving, passes over the exhaust outlets 17 in the cylinder barrel 3, and traps the air in the remaining portion of the cylinder. This trapped air compresses and acts as a cushion. The needle valve by-pass prevents the piston 8 from bouncing back from its cushion of trapped air and accordingly allows it to bleed out and slow the piston 8 to a stop.

It should be noted that the piston rings 14 are for the purpose of trapping air for cushioning. The actual pressure-tight seal of piston 8 inside of cylinder barrel 3 is accomplished by the use of neoprene cups because these are located at the center of the piston and do not pass over the exhaust outlets 17, and consequently do not allow the pressure to escape. Thus the basis for the cushion provided by this invention is the type of a three-way combination of a metallic piston ring which can pass over the exhaust outlets, and neoprene cups for sealing which do not pass over the exhaust outlets, plus the fact that the exhaust outlets are located in the cylinder barrel itself.

From the foregoing it will now be seen that there is herein provided an improved fluid pressure actuated reciprocating motor and cushion means therefor which accomplishes all the objects of the instant invention, and others, including many advantagesof great practical utility and commercial importance.

As many embodiments may be made in this inventive concept, and as many modifications'may be made of the embodiments hereinbefore shown and described, it is to be understood that all matter herein is to be interpreted merely as illustrative, and not in a limiting sense.

I claim:

In a fluid pressure cylinder, a reciprocable piston and a rod, a cylinder chamber in which said piston and rod reciprocate, cylinder heads having flanged portions telescopically mounted on the ends of said cylinder, fluid pressure inletoutlet means in said cylinder heads in communication with the interior of said cylinder, circumferentially disposed fluid pressure outlet means in said cylinder inwardly of each end thereof, portions of the flanges on said cylinder heads defining a recessed area therein in overlying relation to the fluid pressure outlet means in said cylinder, and in communication with said fluid pressure inlet-outlet means in said cylinder heads, said piston closing the outlet means in the cylinder before the end of its stroke to releasably trap a portion of pressure fluid in the end of said cylinder to provide a cushion for said piston, and metered orifices in the flanged portion of said cylinder heads to release said trapped pressure fluid.

References Cited in the file of this patent UNITED STATES PATENTS 1,443,200 Adams Jan. 23, 1923 2,212,998 Crane Aug. 27, 1940 2,558,810 Bent July 3, 1951 2,882,869 Krapf Apr. 21, 1959 2,973,744 Hennells Mar. 7, 1961 

